- Email: [email protected]
Gallnut extract-treated wool and cotton for developing green functional textiles
Dyes and Pigments 103 (2014) 222e227
Contents lists available at ScienceDirect
Dyes and Pigments journal homepage: www.elsevier.com/locate/dyepig
Gallnut extract-treated wool and cotton for developing green functional textiles Eunmi Koh a, Kyung Hwa Hong b, * a b
Department of Food and Nutrition, Seoul Women’s University, Seoul 139-774, South Korea Department of Fashion Design and Merchandising, Kongju National University, Chungnam 314-701, South Korea
a r t i c l e i n f o
a b s t r a c t
Article history: Received 3 June 2013 Received in revised form 4 September 2013 Accepted 11 September 2013 Available online 5 October 2013
Gallnuts are known to exert various pharmaceutical effects, including anti-inflammatory, antimicrobial, antioxidant, and detoxifying effects. In particular, the gallnut extract is thought to be a safe antimicrobial agent for textile application, since it is of natural origin. Hence, wool and cotton fabrics were treated with the gallnut extract, by using a pad-dry-cure process to develop multi-functional clothing material with no harmful effects. Additionally, fabrics were plasma-treated to improve the finishing effect. This study thoroughly investigated the surface appearance, mechanical properties, antimicrobial ability, and antioxidant performance of gallnut extract-treated wool and cotton fabrics. Gallnut extract treatment was found to impose the antimicrobial and antioxidant properties on the wool and cotton fabrics. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Gallnut Cotton Wool Antimicrobial activity Antioxidant ability Plasma
1. Introduction Various antimicrobial technologies have been developed to protect various textile materials from microbial damage, and to prevent cross-transmission of infectious diseases through direct contact. Textiles are known to be susceptible to microbial attack since they have a large surface area and absorb moisture, both of which can promote microbial growth [1]. Moreover, natural fibers allow bacterial growth and multiplication, by providing basic requirements such as nutrients (in the form of protein or cellulose), moisture, and appropriate conditions of oxygen and temperature [2]. Hence, textiles are treated with various compounds, including organic compounds such as triclosan, quaternary ammonium compounds, polybiguanides, N-halamines, chitosan, and inorganic materials such as silver and titanium oxide (TiO2) [3e11], for antimicrobial functionality. The chemicals used in textile treatment include inorganic salts, organometallics, iodophors, phenols, thiophenols, heterocyclics with anionic groups, nitro compounds, urea, formaldehyde derivatives, and amines, among others [8]. Many of these chemicals, however, are toxic to humans and are difficult to degrade naturally [12e15]. Therefore, the development of new and improved
* Corresponding author. Tel.: þ82 41 850 8305; fax: þ82 41 850 8301. E-mail address: [email protected] (K.H. Hong). 0143-7208/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.dyepig.2013.09.015
antimicrobials is an area of active research, and much interest has been generated in development of potential naturally derived antimicrobials [11,16]. Ali and El-Mohamedy reported that wool fabrics dyed with the extract from the red prickly pear plant showed antimicrobial activity against Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, and others [17]. Mahesh et al. found that cotton fabrics treated with a pomegranate extract showed antimicrobial properties that can be attributed to natural tannin compounds present in the extract [18]. Ben-Fadhel et al. reported the manufacture of antibacterial textiles by treating wool and cotton fabrics with an extract of the Eucalyptus leaf [19]. In the previous study, it was recently identified certain natural materials with antimicrobial activity and applied these materials to textiles [2]. Among these natural materials, the gallnut extract was found to be an attractive candidate for textile application, as it displayed excellent antioxidant and antimicrobial activities when applied to textiles. Galls are outgrowths of plant tissues produced when irritants are released by the larvae of gall insects such as those of the Cynipidae family, the gall wasps. This extract contains the highest naturally occurring levels of tannin (gallotannin, 50e75%), as well as smaller molecules such as gallic acid and ellagic acid. Additionally, this extract is known to possess pharmaceutical properties, including anti-inflammatory, antibacterial, and detoxifying properties [20]. Therefore, in this study, the gallnut extract was applied to a wide range of textile materials, including those containing cellulose or
E. Koh, K.H. Hong / Dyes and Pigments 103 (2014) 222e227
protein fibers, by using a pad-dry-cure process. Additionally, it was attempted to improve the finishing effect of the fabric by using the plasma sputtering technique; this technique can modify the textile surface, thus improving the finishing effect of the treatment. 2. Experimental 2.1. Materials Bleached and de-sized cotton fabric (No. 400) was purchased from Testfabrics Inc. (West Pittston, PA); scoured wool fabric (KS K 0905) was purchased from Sombe Co. (Cheongju-si, Korea). Gallnuts were acquired from a local market in Korea in the flake form. 1,1-Diphenyl-2-picrylhydrazyl (DPPH, a free radical generator) was purchased from Calbiochem (Darmstadt, Germany). Methanol (C99.8%) was purchased from Samchun Chemical Co., Ltd (Gyeonggi-do, Korea). All other reagents were used as received, without any further purification. 2.2. Sample preparation 2.2.1. Extraction of natural functional material Gallnuts (100 g) were dried and ground to powder form. Next, the powder was mixed with 1 L of deionized water and boiled for 1 h. The extract was cooled to room temperature and filtered to remove insoluble residues. The resulting filtrate was then diluted to 50 vol %, and the diluted solution was used as a stock finishing solution (pH 4.43) for textile treatment. 2.2.2. Fabric finishing process Cotton and wool fabrics, each cut into pieces approximately 30 cm 30 cm in size, were first treated with plasma for 10 min, by using the CD 400 MC/PC system (Europlasma, Oudenaarde, Belgium) and the gases O2 (under 100 sccm, 40 mTorr, 200 W) and Ar (300 sccm, 40 mTorr, 250 W). Immediately (within 1 h) after plasma treatment, fabrics were processed using the following procedure: they were immersed in the gallnut extract for 30 min (bath ratio ¼ 1:18), the damped fabrics were squeezed through a laboratory padder until a wet pick-up rate of approximately 100% was reached, and then, they were wet-fixed by placement in plastic sealing bags. The storage bags were placed in a convection oven for 30 min at 60 C. Subsequently, the fabrics were cured at 120 C for 15 min, and then washed with deionized water and tumble-dried. 2.3. Characterization The surface morphologies of the fabric samples were examined using a high-resolution field emission scanning microscope (Tescan, Brno, Czech Republic). Color changes, estimated using the L*, a*, and b* values, and yellowness (ASTM E 313) in the treated fabrics were obtained using the Color i7 Benchtop Spectrophotometer (Xrite Inc., Seoul, Korea). Fourier transform infrared (FTIR) spectroscopy was performed using the Spectrum 100 Optica FTIR instrument (PerkinElmer, Waltham, MA), with a resolution of 4 cm1. Measurements were carried out using an attenuated total reflectance (ATR) technique. The tensile strength of the fabrics was measured by the cut strip method (KS K 0520-1995), using the Instron 5543 system (Norwood, MA). The ability of the fabric samples to impede microbial growth and retention was tested using Staphylococcus aureus (ATCC 6538; a gram-positive bacterium) and Klebsiella pneumoniae (ATCC 4352; a gram-negative bacterium) cultures, according to an established protocol to test the antibacterial activity of textiles (KS K 0693). During the antimicrobial test, all fabrics were inoculated with bacteria cultures, and then incubated under ambient conditions for 18 h. After the time allotted for
223
contact had elapsed, the inoculated fabrics were immersed in 20 mL of quenching solution (distilled water), and the containers were strongly agitated to transfer the bacteria from the fabric to the quenching solution. Next, the fabrics were removed, and 1 mL of the quenching solution containing the transferred bacteria was serially 10-fold diluted with distilled water. A fixed volume of each dilution (100 mL) was inoculated on agar plates and the plates were incubated at 35 C for 24 h. Bacterial reduction was calculated according to the following equation:
Reduction of bacteria ð%Þ ¼
ðB AÞ 100 ðBÞ
(1)
In the above equation, A and B represent the surviving bacterial cells (colony-forming unit mL1) on the plates inoculated with test samples derived from treatment of gallnut extract-treated fabrics and the control untreated fabrics, respectively. The dyed cotton fabrics were exposed to DPPH radicals (DPPH) to measure the antioxidant activity, using a previously reported method [21]. DPPH is a well-known radical and acts as a trap (“scavenger”) for other radicals. Therefore, a reduction in the reaction rate upon the addition of DPPH is used as an indicator of the radical nature of that reaction [22]. The evaluation was conducted as follows: 500 mg of the fabric was immersed in a container containing 30 mL of 0.15 mM DPPH/methanol solution. After the solution had been allowed to stand in the dark for 1 h, the absorbance at 517 nm was measured using a UVeVis spectrophotometer (SINCO S-3100; SCINCO Co., Ltd. Seoul, Korea). A reduction in the absorbance of the reaction mixture indicated a higher DPPH scavenging activity. DPPH scavenging activity was calculated using the following equation:
DPPH$scavenging activity ð%Þ ¼
CS 100 C
(2)
In the above equation, S and C represent the absorbance of sample and control, respectively. 3. Results and discussion 3.1. Surface appearance of gallnut extract-treated fabrics Table 1 shows the color properties of wool and cotton fabrics after gallnut extract treatment. The three coordinates of CIELAB represent the color shade (L* ¼ 0 indicates black, while L* ¼ 100 indicates a diffuse white color; the L* value for specular-white may be higher), the color position between red/magenta and green (negative a* values indicate green, while positive a* values indicate magenta), and its position between yellow and blue (negative b* values indicate blue, while positive values indicate yellow) [23]. Additionally, the yellowness index indicates a yellow shade detected on the fabric surface. Overall, following treatment of both cotton and wool fabrics with the gallnut extract, a* and b* values as well as the yellowness index increased, while L* values decreased.
Table 1 Color appearance of wool and cotton fabrics.
Untreated wool Gallnut-treated wool Ar plasma þ gallnut-treated wool O2 plasma þ gallnut-treated wool Untreated cotton Gallnut-treated cotton Ar plasma þ gallnut-treated cotton O2 plasma þ gallnut-treated cotton
L*
a*
b*
Yellowness index
88.87 84.24 83.86 84.21 94.99 90.90 91.25 91.21
1.16 1.45 1.20 1.29 0.52 0.28 0.29 0.27
12.63 14.52 15.25 14.80 3.25 9.67 9.73 9.29
19.24 23.12 24.25 23.48 4.85 14.80 14.86 14.22
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Fig. 1. SEM images of wool fibers; (a) untreated wool, (b) gallnut extract-treated wool, (c) Ar plasma þ gallnut extract-treated wool, (d) O2 plasma þ gallnut extract-treated wool.
Fig. 2. SEM images of cotton fibers; (a) untreated cotton, (b) gallnut extract-treated cotton, (c) Ar plasma þ gallnut extract-treated cotton, (d) O2 plasma þ gallnut extract-treated cotton.
E. Koh, K.H. Hong / Dyes and Pigments 103 (2014) 222e227
Fig. 3. FTIR spectra of wool fabrics; (a) untreated wool, (b) gallnut extract-treated wool, (c) Ar plasma þ gallnut extract-treated wool, (d) O2 plasma þ gallnut extracttreated wool.
This indicates that the fabrics became somewhat darker and yellowish after treatment with gallnut extract. This could be attributed to the naturally brown colorants (such as ellagic acid) present in the gallnut extract, which have been used as natural pigments for fabric dyeing in Asia [24e26]. The surface morphology of the wool and cotton fibers is shown in Figs. 1 and 2. As shown in Fig. 1, the wool scale was damaged by plasma treatments; however, no significant differences were detected between Ar plasmatreated wool (Fig. 1(c)) and O2 plasma-treated wool (Fig. 1(d)). Plasma treatment of the cotton fibers allowed the gallnut extract to adhere evenly to the surface of the fiber during treatment. 3.2. Examination of the chemical properties of gallnut extracttreated fabrics The FTIR spectra of wool and cotton fabrics are shown in Figs. 3 and 4. Wool fibers are composed of more than 18 amino acids. The main functional groups include carboxyl (eCOOH), amino (e NH2), and hydroxyl (eOH) groups [27]. Overall, as shown in Fig. 3, all wool fibers exhibited similar absorption at the following wavelengths: 3280 cm1 (NeH and OeH), 2871 cm1 (eCH2), 1632 cm1 (amide I), 1518 cm1 (amide II), and 1233 cm1 (amide
Fig. 4. FTIR spectra of cotton fabrics; (a) untreated cotton, (b) gallnut extract-treated cotton, (c) Ar plasma þ gallnut extract-treated cotton, (d) O2 plasma þ gallnut extract-treated cotton.
225
III). However, new peaks at 1314 cm1 and 1044 cm1 were observed in the spectra of gallnut extract-treated wool fabrics (Fig. 3(b)e(d)). This observation may be attributable to ester CeO stretching, caused by ester bond formation between the eOH group in certain amino acids such as serine and the eCOOH group of gallic acid. All cotton fabrics (see Fig. 4) showed a 1314 cm1 band that was associated with the bending vibration mode of hydrocarbon structures, as well as 1361 cm1 and 1430 cm1 bands associated with symmetric stretching of carboxylates, which originate from cellulosic molecules. However, it was found that the cellulose hydroxyl peak at approximately 1635 cm1 was split into 2 peaks at 1718 cm1 and 1618 cm1 after gallnut extract treatment (Fig. 4(b)e (d)). Additionally, it was suspected that these peaks were generated by the vibration of the carbonyl C]O double bond and the aromatic C]C double bond stretch that originated from gallic acid. Thus, gallotannin, which is a type of hydrolysable tannin that is a major constituent of gallnut, may be easily hydrolyzed to yield gallic acid under the weakly acidic treatment conditions (pH 4.43) [28]. Gallic acid may have been incorporated into cotton fabrics by ester bond formation between the cellulose eOH group of cotton fibers and the eCOOH group of gallic acid. However, the peak generated by ester CeO stretching was not identified in the FTIR spectra because it overlapped with that generated by the ether CeOeC stretching of cellulose at 1000e1300 cm1 [28]. However, the plasma treatment did not significantly affect either the wool or the cotton fabric. 3.3. Examination of the mechanical properties of the gallnut extract-treated fabrics The tensile strength of the cotton and wool fabrics is shown in Fig. 5. Overall, the tensile strength of the woolen fabric significantly increased after gallnut extract treatment. This may be because gallotannin residues crosslinked with certain amino acids in the protein chains of wool fibers in wool. Tannins are large polyphenolic compounds that contain a sufficient number of hydroxyl and other (such as the carboxyl) groups to form strong bonds or complexes with proteins and other macromolecules. Thus, gallotannin in the gallnut extract enhanced the mechanical properties of wool fiber by forming chemical bonds with basic amino acids in wool protein chains [29,30]. According to previous studies, tannine protein interactions are most frequently based on hydrophobic and hydrogen bonding, and the interaction between the protein and the tannin is pH-dependent; each protein has a distinctive optimum pH [31,32]. The tensile strength of cotton fabrics slightly decreased after gallnut extract treatment. This may be because the acidic
Fig. 5. Tensile strength of wool and cotton fabrics; (a) untreated, (b) gallnut extracttreated, (c) Ar plasma þ gallnut extract-treated, (d) O2 plasma þ gallnut extracttreated.
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Table 2 Antimicrobial properties of wool and cotton fabrics. Reduction % of bacteria
Untreated wool Gallnut-treated wool Ar plasma þ gallnut-treated wool O2 plasma þ gallnut-treated wool Untreated cotton Gallnut treated cotton Ar plasma þ gallnut-treated cotton O2 plasma þ gallnut-treated cotton
S. aureus
K. pneumoniae
e 91.2 99.9 99.9 e 99.9 99.9 99.9
e 78.6 24.9 26.3 e 94.5 92.8 91.9
conditions (pH 4.43) may have resulted in cellulose degradation during gallnut extract treatment. 3.4. Assessment of the antibacterial capacity of gallnut extracttreated fabrics Table 2 shows the antibacterial properties of wool and cotton fabrics treated with S. aureus and K. pneumoniae. Gallnut extract treatment enhanced the antimicrobial activity of cotton fibers. However, the gallnut extract-treated wool fabrics were found to be active against S. aureus, but were relatively inactive against K. pneumoniae. The amount of the gallnut extract retained on the treated wool fabrics may not be sufficient to combat the growth of the gram-negative K. pneumoniae, as gram-negative organisms have an additional lipopolysaccharide-containing outer membrane, unlike gram-positive bacteria [33]. Additionally, plasma treatment increased the hydrophilicity of the wool fabric, and therefore, more bacteria were adsorbed onto the plasma-treated wool fabrics during the antimicrobial testing process. A change in the hydrophilicity of the woolen fabric was observed, as shown in Fig. 6. 3.5. Assessment of the antioxidant ability of the gallnut extracttreated fabrics The antioxidant activity of the gallnut-treated wool and cotton fabrics was also investigated using the DPPH assay. DPPH is a stable radical with a maximum absorption at 517 nm and can readily undergo scavenging by an antioxidant [34]. As indicated in Fig. 7, the antioxidant activities of the wool and cotton fabrics
Fig. 7. Antioxidant activities of wool and cotton fabrics; (a) untreated, (b) gallnut extract-treated, (c) Ar plasma þ gallnut extract-treated, (d) O2 plasma þ gallnut extract-treated.
significantly increased after the gallnut extract treatment. This could be attributed to the retention of gallotannin and its hydrolysable form, gallic acid on the surface of the treated fabrics. Both compounds are phenolic acids, which are reported to act as antioxidants and help protect human cells against oxidative damage [35,36]. 4. Conclusion Multifunctional wool and cotton fabrics showing enhanced antimicrobial and antioxidant activities were successfully produced by treatment with the gallnut extract, by using a pad-dry-cure process. Overall, the fabric appeared yellowish after treatment. Additionally, the tensile strength of the woolen fabric increased after treatment, while that of the cotton fabric decreased. However, cotton fabrics treated with the gallnut extract showed excellent functionality with respect to their antimicrobial capacity and antioxidant activity. Wool fabrics treated with the gallnut extract showed high antioxidant activity and limited antimicrobial capacity. This is because they were found to be active against S. aureus, but were relatively inactive against K. pneumoniae. In contrast, cotreatment with plasma did not significantly alter the gallnut extract effects on the wool or cotton fabrics. Additionally, plasma treatment improved the hydrophilicity of wool and facilitated microbial adsorption to this fabric. Acknowledgment This work was supported by the Research Grant of the Kongju National University in 2013. References
Fig. 6. Images of water drop on wool fabrics; (a) untreated wool, (b) gallnut extracttreated wool, (c) Ar plasma þ gallnut extract-treated wool, (d) O2 plasma þ gallnut extract-treated wool.
[1] Cardamone JM. Proteolytic activity of aspergillus flavus on wool. AATCC Rev 2002;2:30e5. [2] Hong KH, Bae JH, Jin SR, Yang JS. Preparation and properties of multifunctionalized cotton fabrics treated by extracts of gromwell and gallnut. Cellulose 2012;19:507e15. [3] Klueh U, Wagner V, Kelly S, Johnson A, Bryers JD. Efficacy of silver-coated fabric to prevent bacterial colonization and subsequent device-based biofilm formation. J Biomed Mater Res Part B 2000;53:621e31. [4] Lin J, Qiu S, Lewis K, Klibanov AM. Mechanism of bactericidal and fungicidal activities of textiles covalently modified with alkylated polyethylenimine. Biotechnol Bioeng 2003;83:168e72. [5] Sun Y, Sun GJ. Novel refreshable N-halamine polymeric biocides: grafting hydantoin-containing monomers onto high performance fibers by a continuous process. Appl Polym Sci 2003;88:1032e9.
E. Koh, K.H. Hong / Dyes and Pigments 103 (2014) 222e227 [6] Tashiro T. Antibacterial and bacterium adsorbing macromolecules. Macromol Mater Eng 2001;286:63e87. [7] Yuranova T, Rincon AG, Bozzi A, Parra S, Pulgarin C, Albers P, et al. Antibacterial textiles prepared by RF-plasma and vacuum-UV mediated deposition of silver. J Photochem Photobiol A Chem 2003;161:27e34. [8] Gao Y, Cranston R. Recent advances in antimicrobial treatments of textiles. Text Res J 2008;78:60e72. [9] Purwar R, Joshi M. Recent developments in antimicrobial finishing of textiles e a review. AATCC Rev 2004;4:22e6. [10] Simoncic B, Tomsic B. Structure of novel antimicrobial agents for textiles e a review. Text Res J 2010;80:1721e37. [11] Windler L, Height M, Nowack B. Comparative evaluation of antimicrobials for textile applications. Environ Int 2013;53:62e73. [12] Risti c T, Zemlji c LF, Novak M, Kun ci c MK, Sonjak S, Cimerman NG, et al. Antimicrobial efficiency of functionalized cellulose fibres as potential medical textiles. In: Méndez-Vilas A, editor. Science against microbial pathogens: communicating current research and technological advances. Formatex; 2011. p. 36e51. [13] Blaser SA, Scheringer M, MacLeod M, Hungerbuehler K. Estimation of cumulative aquatic exposure and risk due to silver: contribution of nanofunctionalized plastics and textiles. Sci Total Environ 2008;390:396e409. [14] Dann AB, Hontela A. Triclosan: environmental exposure, toxicity and mechanisms of action. J Appl Toxicol 2011;31:285e311. [15] Madsen T, Samsøe-Petersen L, Gustavson K, Rasmussen D. Ecotoxicological assessment of antifouling biocides and nonbiocidal antifouling paints. Environmental Project No. 531. Hørsholm, Denmark: Danish Environmental Protection Agency; 2000. [16] Joshi M, Wazed AS. Ecofriendly antimicrobial finishing of textiles using bioactive agents based on natural products. Indian J Fibre Text Res 2009;34: 295e304. [17] Ali NF, El-Mohamedy RSR. Eco-friendly and protective natural dye from red prickly pear (Opuntia Lasiacantha Pfeiffer) plant. J Saudi Chem Soc 2011;15:257e61. [18] Mahesh S, Manjunatha-Reddy AH, Vijaya-Kumar G. Studies on antimicrobial textile finish using certain plant natural products. ICABPS 2011;1:253e8. [19] Ben Fadhel B, Aissi A, Ladhari N, Deghrigue R, Joly JP. Antibacterial effects of two Tunisian Eucalyptus leaf extracts on wool and cotton fabrics. J Text 2012;103:1197e204.
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[20] Park AY, Kim IY, Song WS. The effect of gallnut mordanting on gromwell dyed silk fabric. J Korean Soc Clothing Text 2009;33:256e65. [21] Han J, Weng XC, Bi KS. Antioxidants from a Chinese medicinal herb: Lithospermum erythrorhizon. Food Chem 2008;106:2e10. [22] Alger MSM. Polymer science dictionary. London, UK: Springer; 1997. p. 152. [23] Schanda J. Colorimetry: understanding the CIE system. Hoboken, New Jersey: Wiley; 2007 [Chapter 3]. [24] Kwak MJ, Kwon JS, Lee SH. Natural dyeing of chitosan crosslinked cotton fabrics (II)-Gallnut-. J Kor Soc Cloth Ind 2008;10:377e84. [25] Hong SJ, Choi IR, Jeon DW, Kim JJ. Effect of chitosan and mordant treatments on the color change of cotton and nylon fabrics dyed using Rhusjara ica. The Res J Costume Culture 2005;13:380e90. [26] Shin NH, Kim SY, Cho KR. A study on using gray color dyeing from gallapple. J Kor Soc Cloth Ind 2005;7:547e52. [27] Hsieh SH, Huang ZK, Huang ZZ, Tseng ZS. Antimicrobial and physical properties of woolen fabrics cured with citric acid and chitosan. J Appl Polym Sci 2004;94:1999e2007. [28] Pavia DL, Lampman GM, Kriz GS. Introduction to spectroscopy. Florida: Harcourt Brace College Publishers; 1996 [Chapter 2]. [29] Zhang X, Do MD. Plasticization and crosslinking effects of acetoneformaldehyde and tannin resins on wheat protein-based natural polymers. Carbohydr Res 2009;344:1180e9. [30] Frazier RA, Deaville ER, Green RJ, Stringano E, Willoughby I, Plant J, et al. Interactions of tea tannins and condensed tannins with proteins. J Pharm Biomed Anal 2010;51:490e5. [31] Haslam E. Plant polyphenols. Vegetable tannins revisited. Cambridge, UK: Cambridge University Press; 1989. [32] Min BR, Barry TN, Attwood GT, McNabb WC. The effect of condensed tannins on the nutrition and health of ruminants fed fresh temperature forages: a review. Anim Feed Sci Technol 2003;106:3e19. [33] http://en.wikipedia.org/wiki/Bacteria [access in March 2013]. [34] Lu YR, Foo YL. Antioxidant activities of polyphenols from sage (Salvia officinalis). Food Chem 2001;75:197e202. [35] Kim YJ. Antimelanogenic and antioxidant properties of gallic acid. Biol Pharm Bull 2007;30:1052e5. [36] http://en.wikipedia.org/wiki/Gallic_acid [access in March 2013].
Contents lists available at ScienceDirect
Dyes and Pigments journal homepage: www.elsevier.com/locate/dyepig
Gallnut extract-treated wool and cotton for developing green functional textiles Eunmi Koh a, Kyung Hwa Hong b, * a b
Department of Food and Nutrition, Seoul Women’s University, Seoul 139-774, South Korea Department of Fashion Design and Merchandising, Kongju National University, Chungnam 314-701, South Korea
a r t i c l e i n f o
a b s t r a c t
Article history: Received 3 June 2013 Received in revised form 4 September 2013 Accepted 11 September 2013 Available online 5 October 2013
Gallnuts are known to exert various pharmaceutical effects, including anti-inflammatory, antimicrobial, antioxidant, and detoxifying effects. In particular, the gallnut extract is thought to be a safe antimicrobial agent for textile application, since it is of natural origin. Hence, wool and cotton fabrics were treated with the gallnut extract, by using a pad-dry-cure process to develop multi-functional clothing material with no harmful effects. Additionally, fabrics were plasma-treated to improve the finishing effect. This study thoroughly investigated the surface appearance, mechanical properties, antimicrobial ability, and antioxidant performance of gallnut extract-treated wool and cotton fabrics. Gallnut extract treatment was found to impose the antimicrobial and antioxidant properties on the wool and cotton fabrics. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Gallnut Cotton Wool Antimicrobial activity Antioxidant ability Plasma
1. Introduction Various antimicrobial technologies have been developed to protect various textile materials from microbial damage, and to prevent cross-transmission of infectious diseases through direct contact. Textiles are known to be susceptible to microbial attack since they have a large surface area and absorb moisture, both of which can promote microbial growth [1]. Moreover, natural fibers allow bacterial growth and multiplication, by providing basic requirements such as nutrients (in the form of protein or cellulose), moisture, and appropriate conditions of oxygen and temperature [2]. Hence, textiles are treated with various compounds, including organic compounds such as triclosan, quaternary ammonium compounds, polybiguanides, N-halamines, chitosan, and inorganic materials such as silver and titanium oxide (TiO2) [3e11], for antimicrobial functionality. The chemicals used in textile treatment include inorganic salts, organometallics, iodophors, phenols, thiophenols, heterocyclics with anionic groups, nitro compounds, urea, formaldehyde derivatives, and amines, among others [8]. Many of these chemicals, however, are toxic to humans and are difficult to degrade naturally [12e15]. Therefore, the development of new and improved
* Corresponding author. Tel.: þ82 41 850 8305; fax: þ82 41 850 8301. E-mail address: [email protected] (K.H. Hong). 0143-7208/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.dyepig.2013.09.015
antimicrobials is an area of active research, and much interest has been generated in development of potential naturally derived antimicrobials [11,16]. Ali and El-Mohamedy reported that wool fabrics dyed with the extract from the red prickly pear plant showed antimicrobial activity against Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, and others [17]. Mahesh et al. found that cotton fabrics treated with a pomegranate extract showed antimicrobial properties that can be attributed to natural tannin compounds present in the extract [18]. Ben-Fadhel et al. reported the manufacture of antibacterial textiles by treating wool and cotton fabrics with an extract of the Eucalyptus leaf [19]. In the previous study, it was recently identified certain natural materials with antimicrobial activity and applied these materials to textiles [2]. Among these natural materials, the gallnut extract was found to be an attractive candidate for textile application, as it displayed excellent antioxidant and antimicrobial activities when applied to textiles. Galls are outgrowths of plant tissues produced when irritants are released by the larvae of gall insects such as those of the Cynipidae family, the gall wasps. This extract contains the highest naturally occurring levels of tannin (gallotannin, 50e75%), as well as smaller molecules such as gallic acid and ellagic acid. Additionally, this extract is known to possess pharmaceutical properties, including anti-inflammatory, antibacterial, and detoxifying properties [20]. Therefore, in this study, the gallnut extract was applied to a wide range of textile materials, including those containing cellulose or
E. Koh, K.H. Hong / Dyes and Pigments 103 (2014) 222e227
protein fibers, by using a pad-dry-cure process. Additionally, it was attempted to improve the finishing effect of the fabric by using the plasma sputtering technique; this technique can modify the textile surface, thus improving the finishing effect of the treatment. 2. Experimental 2.1. Materials Bleached and de-sized cotton fabric (No. 400) was purchased from Testfabrics Inc. (West Pittston, PA); scoured wool fabric (KS K 0905) was purchased from Sombe Co. (Cheongju-si, Korea). Gallnuts were acquired from a local market in Korea in the flake form. 1,1-Diphenyl-2-picrylhydrazyl (DPPH, a free radical generator) was purchased from Calbiochem (Darmstadt, Germany). Methanol (C99.8%) was purchased from Samchun Chemical Co., Ltd (Gyeonggi-do, Korea). All other reagents were used as received, without any further purification. 2.2. Sample preparation 2.2.1. Extraction of natural functional material Gallnuts (100 g) were dried and ground to powder form. Next, the powder was mixed with 1 L of deionized water and boiled for 1 h. The extract was cooled to room temperature and filtered to remove insoluble residues. The resulting filtrate was then diluted to 50 vol %, and the diluted solution was used as a stock finishing solution (pH 4.43) for textile treatment. 2.2.2. Fabric finishing process Cotton and wool fabrics, each cut into pieces approximately 30 cm 30 cm in size, were first treated with plasma for 10 min, by using the CD 400 MC/PC system (Europlasma, Oudenaarde, Belgium) and the gases O2 (under 100 sccm, 40 mTorr, 200 W) and Ar (300 sccm, 40 mTorr, 250 W). Immediately (within 1 h) after plasma treatment, fabrics were processed using the following procedure: they were immersed in the gallnut extract for 30 min (bath ratio ¼ 1:18), the damped fabrics were squeezed through a laboratory padder until a wet pick-up rate of approximately 100% was reached, and then, they were wet-fixed by placement in plastic sealing bags. The storage bags were placed in a convection oven for 30 min at 60 C. Subsequently, the fabrics were cured at 120 C for 15 min, and then washed with deionized water and tumble-dried. 2.3. Characterization The surface morphologies of the fabric samples were examined using a high-resolution field emission scanning microscope (Tescan, Brno, Czech Republic). Color changes, estimated using the L*, a*, and b* values, and yellowness (ASTM E 313) in the treated fabrics were obtained using the Color i7 Benchtop Spectrophotometer (Xrite Inc., Seoul, Korea). Fourier transform infrared (FTIR) spectroscopy was performed using the Spectrum 100 Optica FTIR instrument (PerkinElmer, Waltham, MA), with a resolution of 4 cm1. Measurements were carried out using an attenuated total reflectance (ATR) technique. The tensile strength of the fabrics was measured by the cut strip method (KS K 0520-1995), using the Instron 5543 system (Norwood, MA). The ability of the fabric samples to impede microbial growth and retention was tested using Staphylococcus aureus (ATCC 6538; a gram-positive bacterium) and Klebsiella pneumoniae (ATCC 4352; a gram-negative bacterium) cultures, according to an established protocol to test the antibacterial activity of textiles (KS K 0693). During the antimicrobial test, all fabrics were inoculated with bacteria cultures, and then incubated under ambient conditions for 18 h. After the time allotted for
223
contact had elapsed, the inoculated fabrics were immersed in 20 mL of quenching solution (distilled water), and the containers were strongly agitated to transfer the bacteria from the fabric to the quenching solution. Next, the fabrics were removed, and 1 mL of the quenching solution containing the transferred bacteria was serially 10-fold diluted with distilled water. A fixed volume of each dilution (100 mL) was inoculated on agar plates and the plates were incubated at 35 C for 24 h. Bacterial reduction was calculated according to the following equation:
Reduction of bacteria ð%Þ ¼
ðB AÞ 100 ðBÞ
(1)
In the above equation, A and B represent the surviving bacterial cells (colony-forming unit mL1) on the plates inoculated with test samples derived from treatment of gallnut extract-treated fabrics and the control untreated fabrics, respectively. The dyed cotton fabrics were exposed to DPPH radicals (DPPH) to measure the antioxidant activity, using a previously reported method [21]. DPPH is a well-known radical and acts as a trap (“scavenger”) for other radicals. Therefore, a reduction in the reaction rate upon the addition of DPPH is used as an indicator of the radical nature of that reaction [22]. The evaluation was conducted as follows: 500 mg of the fabric was immersed in a container containing 30 mL of 0.15 mM DPPH/methanol solution. After the solution had been allowed to stand in the dark for 1 h, the absorbance at 517 nm was measured using a UVeVis spectrophotometer (SINCO S-3100; SCINCO Co., Ltd. Seoul, Korea). A reduction in the absorbance of the reaction mixture indicated a higher DPPH scavenging activity. DPPH scavenging activity was calculated using the following equation:
DPPH$scavenging activity ð%Þ ¼
CS 100 C
(2)
In the above equation, S and C represent the absorbance of sample and control, respectively. 3. Results and discussion 3.1. Surface appearance of gallnut extract-treated fabrics Table 1 shows the color properties of wool and cotton fabrics after gallnut extract treatment. The three coordinates of CIELAB represent the color shade (L* ¼ 0 indicates black, while L* ¼ 100 indicates a diffuse white color; the L* value for specular-white may be higher), the color position between red/magenta and green (negative a* values indicate green, while positive a* values indicate magenta), and its position between yellow and blue (negative b* values indicate blue, while positive values indicate yellow) [23]. Additionally, the yellowness index indicates a yellow shade detected on the fabric surface. Overall, following treatment of both cotton and wool fabrics with the gallnut extract, a* and b* values as well as the yellowness index increased, while L* values decreased.
Table 1 Color appearance of wool and cotton fabrics.
Untreated wool Gallnut-treated wool Ar plasma þ gallnut-treated wool O2 plasma þ gallnut-treated wool Untreated cotton Gallnut-treated cotton Ar plasma þ gallnut-treated cotton O2 plasma þ gallnut-treated cotton
L*
a*
b*
Yellowness index
88.87 84.24 83.86 84.21 94.99 90.90 91.25 91.21
1.16 1.45 1.20 1.29 0.52 0.28 0.29 0.27
12.63 14.52 15.25 14.80 3.25 9.67 9.73 9.29
19.24 23.12 24.25 23.48 4.85 14.80 14.86 14.22
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Fig. 1. SEM images of wool fibers; (a) untreated wool, (b) gallnut extract-treated wool, (c) Ar plasma þ gallnut extract-treated wool, (d) O2 plasma þ gallnut extract-treated wool.
Fig. 2. SEM images of cotton fibers; (a) untreated cotton, (b) gallnut extract-treated cotton, (c) Ar plasma þ gallnut extract-treated cotton, (d) O2 plasma þ gallnut extract-treated cotton.
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Fig. 3. FTIR spectra of wool fabrics; (a) untreated wool, (b) gallnut extract-treated wool, (c) Ar plasma þ gallnut extract-treated wool, (d) O2 plasma þ gallnut extracttreated wool.
This indicates that the fabrics became somewhat darker and yellowish after treatment with gallnut extract. This could be attributed to the naturally brown colorants (such as ellagic acid) present in the gallnut extract, which have been used as natural pigments for fabric dyeing in Asia [24e26]. The surface morphology of the wool and cotton fibers is shown in Figs. 1 and 2. As shown in Fig. 1, the wool scale was damaged by plasma treatments; however, no significant differences were detected between Ar plasmatreated wool (Fig. 1(c)) and O2 plasma-treated wool (Fig. 1(d)). Plasma treatment of the cotton fibers allowed the gallnut extract to adhere evenly to the surface of the fiber during treatment. 3.2. Examination of the chemical properties of gallnut extracttreated fabrics The FTIR spectra of wool and cotton fabrics are shown in Figs. 3 and 4. Wool fibers are composed of more than 18 amino acids. The main functional groups include carboxyl (eCOOH), amino (e NH2), and hydroxyl (eOH) groups [27]. Overall, as shown in Fig. 3, all wool fibers exhibited similar absorption at the following wavelengths: 3280 cm1 (NeH and OeH), 2871 cm1 (eCH2), 1632 cm1 (amide I), 1518 cm1 (amide II), and 1233 cm1 (amide
Fig. 4. FTIR spectra of cotton fabrics; (a) untreated cotton, (b) gallnut extract-treated cotton, (c) Ar plasma þ gallnut extract-treated cotton, (d) O2 plasma þ gallnut extract-treated cotton.
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III). However, new peaks at 1314 cm1 and 1044 cm1 were observed in the spectra of gallnut extract-treated wool fabrics (Fig. 3(b)e(d)). This observation may be attributable to ester CeO stretching, caused by ester bond formation between the eOH group in certain amino acids such as serine and the eCOOH group of gallic acid. All cotton fabrics (see Fig. 4) showed a 1314 cm1 band that was associated with the bending vibration mode of hydrocarbon structures, as well as 1361 cm1 and 1430 cm1 bands associated with symmetric stretching of carboxylates, which originate from cellulosic molecules. However, it was found that the cellulose hydroxyl peak at approximately 1635 cm1 was split into 2 peaks at 1718 cm1 and 1618 cm1 after gallnut extract treatment (Fig. 4(b)e (d)). Additionally, it was suspected that these peaks were generated by the vibration of the carbonyl C]O double bond and the aromatic C]C double bond stretch that originated from gallic acid. Thus, gallotannin, which is a type of hydrolysable tannin that is a major constituent of gallnut, may be easily hydrolyzed to yield gallic acid under the weakly acidic treatment conditions (pH 4.43) [28]. Gallic acid may have been incorporated into cotton fabrics by ester bond formation between the cellulose eOH group of cotton fibers and the eCOOH group of gallic acid. However, the peak generated by ester CeO stretching was not identified in the FTIR spectra because it overlapped with that generated by the ether CeOeC stretching of cellulose at 1000e1300 cm1 [28]. However, the plasma treatment did not significantly affect either the wool or the cotton fabric. 3.3. Examination of the mechanical properties of the gallnut extract-treated fabrics The tensile strength of the cotton and wool fabrics is shown in Fig. 5. Overall, the tensile strength of the woolen fabric significantly increased after gallnut extract treatment. This may be because gallotannin residues crosslinked with certain amino acids in the protein chains of wool fibers in wool. Tannins are large polyphenolic compounds that contain a sufficient number of hydroxyl and other (such as the carboxyl) groups to form strong bonds or complexes with proteins and other macromolecules. Thus, gallotannin in the gallnut extract enhanced the mechanical properties of wool fiber by forming chemical bonds with basic amino acids in wool protein chains [29,30]. According to previous studies, tannine protein interactions are most frequently based on hydrophobic and hydrogen bonding, and the interaction between the protein and the tannin is pH-dependent; each protein has a distinctive optimum pH [31,32]. The tensile strength of cotton fabrics slightly decreased after gallnut extract treatment. This may be because the acidic
Fig. 5. Tensile strength of wool and cotton fabrics; (a) untreated, (b) gallnut extracttreated, (c) Ar plasma þ gallnut extract-treated, (d) O2 plasma þ gallnut extracttreated.
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Table 2 Antimicrobial properties of wool and cotton fabrics. Reduction % of bacteria
Untreated wool Gallnut-treated wool Ar plasma þ gallnut-treated wool O2 plasma þ gallnut-treated wool Untreated cotton Gallnut treated cotton Ar plasma þ gallnut-treated cotton O2 plasma þ gallnut-treated cotton
S. aureus
K. pneumoniae
e 91.2 99.9 99.9 e 99.9 99.9 99.9
e 78.6 24.9 26.3 e 94.5 92.8 91.9
conditions (pH 4.43) may have resulted in cellulose degradation during gallnut extract treatment. 3.4. Assessment of the antibacterial capacity of gallnut extracttreated fabrics Table 2 shows the antibacterial properties of wool and cotton fabrics treated with S. aureus and K. pneumoniae. Gallnut extract treatment enhanced the antimicrobial activity of cotton fibers. However, the gallnut extract-treated wool fabrics were found to be active against S. aureus, but were relatively inactive against K. pneumoniae. The amount of the gallnut extract retained on the treated wool fabrics may not be sufficient to combat the growth of the gram-negative K. pneumoniae, as gram-negative organisms have an additional lipopolysaccharide-containing outer membrane, unlike gram-positive bacteria [33]. Additionally, plasma treatment increased the hydrophilicity of the wool fabric, and therefore, more bacteria were adsorbed onto the plasma-treated wool fabrics during the antimicrobial testing process. A change in the hydrophilicity of the woolen fabric was observed, as shown in Fig. 6. 3.5. Assessment of the antioxidant ability of the gallnut extracttreated fabrics The antioxidant activity of the gallnut-treated wool and cotton fabrics was also investigated using the DPPH assay. DPPH is a stable radical with a maximum absorption at 517 nm and can readily undergo scavenging by an antioxidant [34]. As indicated in Fig. 7, the antioxidant activities of the wool and cotton fabrics
Fig. 7. Antioxidant activities of wool and cotton fabrics; (a) untreated, (b) gallnut extract-treated, (c) Ar plasma þ gallnut extract-treated, (d) O2 plasma þ gallnut extract-treated.
significantly increased after the gallnut extract treatment. This could be attributed to the retention of gallotannin and its hydrolysable form, gallic acid on the surface of the treated fabrics. Both compounds are phenolic acids, which are reported to act as antioxidants and help protect human cells against oxidative damage [35,36]. 4. Conclusion Multifunctional wool and cotton fabrics showing enhanced antimicrobial and antioxidant activities were successfully produced by treatment with the gallnut extract, by using a pad-dry-cure process. Overall, the fabric appeared yellowish after treatment. Additionally, the tensile strength of the woolen fabric increased after treatment, while that of the cotton fabric decreased. However, cotton fabrics treated with the gallnut extract showed excellent functionality with respect to their antimicrobial capacity and antioxidant activity. Wool fabrics treated with the gallnut extract showed high antioxidant activity and limited antimicrobial capacity. This is because they were found to be active against S. aureus, but were relatively inactive against K. pneumoniae. In contrast, cotreatment with plasma did not significantly alter the gallnut extract effects on the wool or cotton fabrics. Additionally, plasma treatment improved the hydrophilicity of wool and facilitated microbial adsorption to this fabric. Acknowledgment This work was supported by the Research Grant of the Kongju National University in 2013. References
Fig. 6. Images of water drop on wool fabrics; (a) untreated wool, (b) gallnut extracttreated wool, (c) Ar plasma þ gallnut extract-treated wool, (d) O2 plasma þ gallnut extract-treated wool.
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